Growth stimulating wound dressing with improved contact surfaces

ABSTRACT

A wound contact device comprising a permeable material and a wound contact layer having voids extending through the contact layer to a depth in the permeable material. The wound contact layer can comprise a thin sheet or film forming a generally flat and smooth wound contact surface having essentially no discontinuities or gaps. The wound contact layer can comprise a thin sheet of highly calendered fabric forming a wound contact surface having a mean surface roughness in the range of about 0 microns to about 200 microns. In progressive wound healing, an embodiment of the wound contact device having the fabric contact surface is used in earlier healing stages and an embodiment of the wound contact device with film contact surface is used in later healing stages. The wound contact device is particularly useful in wound dressings for use in suction-assisted wound therapy.

REFERENCE TO RELATED APPLICATIONS

This divisional application claims the benefit under 35 U.S.C. §121 ofapplication Ser. No. 11/825,397, filed on Jul. 6, 2007, entitled GROWTHSTIMULATING WOUND DRESSING WITH IMPROVED CONTACT SURFACES, which takesits priority both under 35 U.S.C. §119(e) of Provisional PatentApplication No. 60/819,146 filed Jul. 7, 2006 and under 35 U.S.C. §120,as a continuation-in-part application, of U.S. patent application Ser.No. 10/982,346, now U.S. Pat. No. 7,884,258, issued Feb. 8, 2011,entitled WOUND CONTACT DEVICE, which in turn claims the benefit under 35U.S.C. §119(e) of Provisional Patent Application No. 60/561,745, filedon Apr. 13, 2004, entitled WOUND CONTACT LAYER FOR USE WITH SUCTION, thecontents all of which are incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to the general field of bandages and other woundcovers. More particularly, the invention relates to the field of woundcontact devices that are placed in direct contact with a wound underbandages or under sealing covers for use in suction-assisted or negativepressure wound therapy.

BACKGROUND OF THE INVENTION

Wound healing is a basic reparative process. It has been knownthroughout time that dressing wounds with appropriate materials aids thenatural regenerative process. Historically, such materials have beenmade from cotton fibers such as gauze. These dressings are beneficial tothe healing process because they insulate damaged tissue from externalcontaminants and because they remove potentially deleterious woundexudates.

As science and medicine have advanced, the technology incorporated intowound healing devices has improved substantially. Highly absorbent woundcontact devices capable of absorbing many times their weight in liquidsare available. Systems that temporarily seal wounds and utilize suctionto remove exudates have found widespread utilization. Devicesincorporating anti-microbial agents and biologic healing agents arecommon. Devices that provide a moist wound environment for improvedhealing have been found to be useful.

Nevertheless, many common conventional and state-of-the-art woundcontact devices have shortcomings, particular for use in suction woundtherapy. In an example, gauze and other similar flat fabric materialsare commonly used in wound dressings. When gauze in contact with a woundbecomes wet with wound exudates, it becomes soggy and soft, losing anystructure it may have had and leaving little or no space above the woundsurface for new tissue growth to occur. When suction is applied to agauze wound dressing, the dressing is compressed into a flattened stateand any space between the gauze fibers is effectively eliminated.Additionally, even when wound exudates are being removed by suction froma gauze dressing, the gauze remains saturated and pressed against thewound, leaving no space above the wound and thus inhibiting new tissuegrowth.

In another example, a dressing using a foam material in contact with thewound retains only a minimal amount of small pores at the wound contactsurface when suction is applied to the dressing. When a foam dressing isused with suction, the pores of the foam collapse, eliminating spaceabove the wound surface. Absent significant open space above the woundsurface, new tissue grows into the foam. Routine removal of the foamdressing causes disruption of new tissue, excessive bleeding, andunnecessary discomfort to the patient. In-growth of tissue into foam isa significant problem because the tissue has nowhere to grow but intothe collapsed cell or pore structure of the foam.

In another example, a dressing using a wound contact device in the formof a relatively rigid perforated sheet, such as an Aquaplast sheet, as asubstrate in contact with the wound, is not sufficiently flexible andconformable to comfortably and adequately conform to wound surfaces thatare often irregular in contour. A dressing having such an inflexible orrigid structured material or wound contact layer causes unnecessary painand discomfort in a patient. In addition, an Aquaplast or similar sheetis constructed from solid plastic with large holes punched into theplastic. Such a sheet does not have small interconnecting intersticesthat facilitate the transport of liquid wound exudates away from thesurface of the wound. The holes in the Aquaplast sheet simply createreservoirs where deleterious wound exudates can pool and impeded woundhealing. Because these large holes do not fluidically communicate witheach other, fluid removal is not practical. In addition, an Aquaplastsheet does not provide any wicking for the effective removal of woundexudates. Further, an Aquaplast sheet is not permeable to either gas orliquids, and thus does not permit a wound to breath in the places wherethe sheet material is in contact with the wound surface, nor does itenable efficient transport of fluids and wound exudates away from thewound.

A wound dressing for use in suction wound therapy preferably has some orall of the following characteristics and properties: the dressing shouldbe flexible and conformable to the wound, the dressing shouldeffectively enable transport of wound exudates away from the woundsurface, and the dressing should allow sufficient voids above the woundwhen suction is applied for unobstructed new tissue growth. The dressingshould maintain structural integrity when moist and should have ageometry to actively encourage tissue growth. When used in the laterstages of tissue regeneration, the dressing should inhibit or minimizeentanglement of healthy new tissue into the dressing material. Early inthe treatment of some wounds, there may be necrotic or dead tissue inthe wound. This dead tissue can be a source of nourishment fordeleterious bacteria. A dressing for treating such wounds may have awound contact surface adapted to debride or remove dead tissue out ofthe wound.

As described in U.S. patent application Ser. No. 10/982,346, commonlyassigned with this application and from which this application is acontinuation in part, wound dressings and wound contact devices havebeen developed to replace traditional gauze or foam pads under woundbandages or wound sealing covers used in suction assisted wound healing.The goal has been to enhance the healing process though the propertiesand geometries of wound contact devices.

One such wound contact device comprises a permeable material having aplurality of dimple voids formed in the wound contact side of thedevice, wherein the dimple voids are preferably disposed in a randomlyspaced pattern. Because the contact device comprises a permeablematerial with interconnecting interstices, it can effectively transportdeleterious wound exudates away from the wound surface. The device canbe cut to size for a wound, and the cut piece place in contact with thetissue of the wound under a bandage or under a sealing cover. The dimplevoids provide empty space into which new tissue can grow withoutbecoming excessively intertwined with the permeable material, incontrast to the intertwining growth that is known to occur with porousfoam pads. The contact elements between the dimple voids provide a maintissue contact surface. The permeable material of the contact deviceprovides sufficient resistance to compression to keep the dimple voidsfrom entirely collapsing when suction or other compacting pressure isapplied to the wound dressing. Additionally, the contact devicemaintains the dimple voids in the presence of moisture.

In addition to providing empty growth space, the combination of thedimple voids and the contact elements imposes a beneficial strain on thetissue when suction is applied to the wound dressing, pulling the tissueinto a catenary-like shape within the voids. These forces and theresulting strain imposed on the tissue are believed to stimulate newtissue growth more effectively than the forces obtained in suctiontherapy using wound dressings that have generally flat surfaces whensuction is applied.

It would be advantageous to provide an improved wound contact devicecomprising a permeable structured material and a wound contact layeraffixed to a side of the structured material forming a wound contactsurface, with a plurality of voids extending through the contact layerto a depth within the structured material and defining wound contactelements on the wound contact surface. In one embodiment, it would beadvantageous to provide a wound contact device having a wound contactsurface adapted to prevent healthy tissue growth from becoming entanglewith the device. In another example, it would be advantageous to providea wound contact device having a wound contact surface adapted to debridedead tissue out of a wound so that revascularized healthy tissue cangrow. The nature of these improvements and the benefits they confer willbe apparent from the description and sample embodiments which appearbelow.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a wound contact device for use in a wounddressing. The device is particularly adapted for use in a dressing wheresuction or negative pressure therapy is used to promote healing. Thewound contact device comprises a permeable material having a woundcontact surface, the wound contact surface comprising a plurality ofdepressions and/or voids interposed between a plurality of wound contactelements. The material may include a plurality of fibers coupled to oneanother. The material may alternatively include a polyester feltmaterial.

An embodiment of the present invention provides a wound contact devicecomprising a thin film affixed to the permeable material for forming thewound contact surface, the thin film covering the wound contact elementsand having apertures corresponding to the depressions or voids, the thinfilm being essentially smooth (i.e., having essentially no surface gaps)so as to resist entanglement with new tissue growth. Another embodimentof the present invention provides a wound contact device comprising athin fabric layer affixed to the permeable material for forming thewound contact surface, the fabric layer covering the wound contactelements and having apertures corresponding to the depressions or voids,the fabric layer having small gaps or openings so as to enableentanglement with and debriding of necrotic tissue, the openings beingsmaller than the voids in the wound contact device.

These and other aspects and objects will become apparent from thefollowing description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitutea part of this specification, illustrate preferred embodiments of theinvention, and together with the general description given above and thedetailed description given below, serve to explain features of theinvention.

FIG. 1 is a perspective view of a channeled wound contact deviceaccording to an exemplary embodiment of the present invention.

FIG. 2A is a perspective view of a channeled wound contact compositeaccording to an exemplary embodiment of the present invention.

FIG. 2B is a cross section of the channeled wound contact composite ofFIG. 2A.

FIG. 3A is a perspective view of a dimpled wound contact deviceaccording an exemplary embodiment of the present invention.

FIG. 3B is a top view of the dimpled wound contact device of FIG. 3A.

FIG. 3C is a bottom view of the dimpled wound contact device of FIG. 3A.

FIG. 3D is a cross sectional view of the dimpled wound contact device ofFIG. 3A.

FIG. 3E is an expanded view showing in detail one dimple of the dimpledwound contact device of FIG. 3A.

FIGS. 4A, 4B, 4C illustrate a method of using the dimpled wound contactdevice of FIG. 3A.

FIG. 5A is a perspective view of an irregular wound contact deviceaccording to an exemplary embodiment of the present invention.

FIG. 5B is a cross sectional view of the irregular wound contact deviceof FIG. 5A.

FIG. 6 is a perspective view of a dimpled wound contact device accordingto an exemplary embodiment of the present invention.

FIG. 7 is a perspective view of a would contact device according to anexemplary embodiment of the present invention.

FIG. 8 is a perspective view of a wound contact device according to anexemplary embodiment of the present invention.

FIG. 9A is a perspective view of a dimpled wound contact deviceaccording an exemplary embodiment of the present invention.

FIG. 9B is a top view of the dimpled wound contact device of FIG. 9A.

FIG. 9C is a bottom view of the dimpled wound contact device of FIG. 9A.

FIG. 9D is a cross sectional view of the dimpled wound contact device ofFIG. 9A.

DETAILED DESCRIPTION OF THE INVENTION

A wound dressing is provided comprising a wound contact device having astructured material and a discontinuous contact surface or layer forpromoting tissue growth. The contact surface or contact layer includeswound contact elements and voids or depressions interposed between thewound contact elements. The structured material maintains the voids whenthe wound contact device is placed against the wound so that the emptyspace or void volume within the voids permits space for tissue growth.

The wound dressing, and in particular the structured material of thewound contact device, is sufficiently physically rugged to resistflattening when forces are imposed to press the wound contact deviceagainst the wound surface. Forces pressing the wound contact deviceagainst the wound surface include, but are not limited to, suctionapplied to the wound dressing during application of negative pressurewound therapy. In addition, the material of the wound contact device,and in particular the structured material, retains its structure whenexposed to aqueous or other bodily fluids, in contrast to manytraditional wound contact device materials that soften and lose theirgeometric form as they moisten.

The structured material of the wound contact device is permeable,allowing the communication of suction proximal to the wound surface andallowing for fluids to be drawn from the wound. The structured materialcan be absorbent, but is able to retain its structure and resist changein the presence of moisture and aqueous liquids.

The voids preferably extend into the structured material to a depth ofat least 0.1 mm above the wound surface when the wound contact device isplaced against the surface of the wound. More preferably, the depth ofthe voids is between about 0.2 mm to about 5 mm. The width of the voids,as defined by the empty space between contact elements adjacent to thevoids, is preferably greater than 0.1 mm. More preferably, the width ofthe voids is between about 0.5 mm to about 10 mm. The voids may be ofany cross-sectional shape, including oblong, round, irregular, orsquare, as shown for example in FIGS. 1A, 3A, 5A, and 8, respectively.In addition, the wound contact elements can be pedestals such that thevoids intersect or are interconnected to form a shape complementary tothe pedestal contact elements, as shown for example in FIG. 7.

Wound healing is recognized as a complex process. When a wound dressingor wound contact device having interposed wound contact elements andvoids, as described herein, is forced against a wound surface, a numberof biological processes are believed to occur, particularly when thewound dressing is subjected to suction. In suction wound therapy with awound contact device or wound dressing as described herein, mechanicalstrain is applied to the underlying tissue. Suction in combination withapertures in the wound contact surface of the wound contact deviceimpose a force resulting in a catenary shape on the tissue, wherebytissue is stretched partially into the voids between the contactelements. The stretched tissue and cells are under strain, which isknown to produce cellular proliferation and migration. Growth of newgranular tissue is further encouraged by removal of excess fluidexudates away from the wound surface by suction. Periodic replacement ofthe wound contact device with another wound contact device havingrandomly spaced dimples, so that different portions of the wound aresuccessively in contact with the contact elements and/or exposed to thevoids, encourages growth throughout the wound surface.

A fibrous material can be used to form the structured material of thewound contact device, the fibrous material having all the flexibilitiesprovided by the textile arts. Fibrous textiles can be formed into astructure suitable for use in a wound contact device by various methods.Among these methods are knitting, weaving, embroidering, braiding,felting, spunbonding, meltblowing, and meltspinning. Each of thesemethods can be further adapted to produce a material having adiscontinuous surface structure including wound contact elements andvoid spaces, as described herein. Such structures can be imparted duringproduction of the textile material by, for example, applying moltenfibers directly to a mold as in meltblowing. Alternatively, thestructures can be formed by working a formed textile material afterproduction by, for example, heat stamping or vacuum forming. Further,fibrous or textile material can be mixed with an adhesive and sprayedonto a textured surface.

The versatility of fibrous textiles also extends to their easyadaptation to composite applications. Individual fiber materials may bevaried to optimize a physical parameter such as rigidity or flexibility.Individual fiber materials can also be selected for their known abilityto assist in wound healing. Examples of such fiber materials are calciumalginate and collagen. Alternatively, fibers may be treated with knownwound healing agents such as hyaluronic acid or antimicrobial silver.The ratio of the fiber materials can be varied to suit the requirementsof the wound. According to one desirable aspect of the invention,different fibers with various wound healing properties may be added asdesired.

A wound contact device comprising fibers also has the advantage of beingsomewhat conformable to the wound surface, which is often irregular.Moreover, fibrous textiles can be formed into structures having numeroussmall interconnected interstices between coupled or intertwined fibers.Such interconnected interstices enable or assist in the transport ofdeleterious wound exudates away from the wound surface. The number,size, and orientation of interstices can be controlled and optimizeddepending on the manufacturing method used to produce the fibrousdevice.

In an example, such as shown in FIG. 3E, the structured material 302comprises intertwined fibers defining interstices or interstitial gapsthroughout. The interstices provide space for liquids and gases to besuctioned from the wound, thus making the structured material generallypermeable. The interstices are smaller than the voids created in thestructured material, based on average cross-sectional area or nominaldiameter. Usually, the interstices are less than half the size of thevoids and are sometimes much smaller than the voids. In a typical woundcontact device 300, as shown in FIGS. 3A to 3E, the voids 304 have adiameter at the wound contact surface 310 in the range of about 1000microns to about 2000 microns. The voids 304 typically penetrate orextend to a depth in the range of about 250 microns to 1000 microns. Incontrast, the interstices or gaps between the fibers throughout thestructured material typically vary from about 0 microns to about 400microns.

Other fibrous structures that are anticipated as beneficial additionsinclude: (1) fluid absorbing fibers; (2) non-adsorbent fibers; (3)bio-absorbable fibers; (4) wicking fibers to wick fluid away from thesurface of the wound; (5) fibers with known healing effects, such ascalcium alginate; (6) bio-erodable fibers for the controlled release ofa curative agent; (7) conductive fibers for the delivery of an electriccharge or current; (8) adherent fibers for the selective removal ofundesirable tissues, substances, or microorganisms; and (9) non-adherentfibers for the protection of delicate tissue.

An exemplary embodiment of a wound contact device is illustrated inFIG. 1. A channeled wound contact device 100 comprises a generallyconformable structured material 102 and includes a wound contact surface110. The structured material 102 is preferably made from a polyestermaterial. The polyester material can include a polyester textile such asa felt, knit, weave, or braid. Creep resistance, as exhibited bypolyester, is particularly desirable, because it enables the structuredmaterial 102 to retain its structure when exposed to moisture and whensubjected to compression due to forces including suction applied to thewound dressing. A felt material such as Masterflow® manufactured by BBAGroup of Wakefield, Mass., has the benefit of interconnectinginterstices that facilitate the transport of liquids away from the woundsurface. The structured material can further include a polyolefin, suchas polyethylene or polypropylene. The structured material can stillfurther include a polyamide such as nylon. The wound contact surface 110is discontinuous, including void channels 104 interspersed between woundcontact elements 106. The void channels 104 extend to a depth into thestructured material 102 to provide empty voids into which new tissue cangrow. The discontinuities or apertures in the wound contact surface 110promote the growth of new tissue.

In use, the channeled wound contact device 100 is pressed against awound into intimate contact with the wound surface. A pressure of 0.1PSI (5 mm Hg) or more, applied by suction or other means, is desirablyapplied to press the wound contact surface 110 against the surface ofthe wound so that the wound contact elements 106 are in intimate contactwith injured tissue and the voids 104 remain clear above the woundsurface to receive new tissue growth. Preferably, suction is applied inthe range of between about 0.25 PSI (12 mm Hg) and about 5 PSI (260 mmHg). More preferably, suction is applied at a level between about 0.67PSI (35 mm Hg) and about 1.45 PSI (75 mm Hg).

FIGS. 2A and 2B illustrate a wound contact device composite 200comprising a channeled contact device 100 and a vapor-permeableadhesive-backed sheet 202. Adhesive-backed vapor-permeable sheets, ingeneral, are known in the art and are believed to contribute to woundhealing by maintaining a moisture level that is optimal for some wounds.In use, the wound contact device composite 200 is placed onto thesurface of the wound with the wound contact surface 110 of the channeledwound contact device 100 in contact with the wound. The adhesive sheet202 covers the wound contact device 100 and adheres to skin adjacent thewound, securing the contact device 100 in the wound and protecting thewound from bacteria and other external contamination and/or abrasion,while allowing for the transmission of moisture vapor from the wound.

FIGS. 3A to 3E illustrate a dimpled wound contact device 300 comprisinga structured material 302 and a wound contact layer 320 having a woundcontact surface 310. When the wound contact device 300 is used to treata wound, the wound contact layer 320 is proximate to the wound and thestructured material 302 is disposed distally therefrom. The structuredmaterial 302 can be constructed using similar materials and productionmethods employed with regard to the channeled wound contact device 100.As illustrated in FIG. 3A, the wound contact layer 320 is preferablyrelatively thin in comparison with the structured material 302. Thewound contact layer 320 can be fused or bonded to a side of theunderlying material 302. Alternatively, the wound contact layer can beintegrally formed with the structured material 302, as shown in FIGS. 9Ato 9D. The wound contact layer 320 and the structured material 302 canbe made from the same material or from different materials.

As best illustrated in FIGS. 3B, 3D and 3E, the wound contact devicecomprises a plurality of dimple voids 304 that are generally surroundedby wound contact elements 306. The dimple voids 304 extend throughapertures 312 in the contact layer 320 and to a depth in the structuredmaterial 302. In particular the voids 304 extend from a first end 304A(FIG. 3E) at the aperture 312 to a second end 304B in the structuredmaterial 302, with the first end 304 comprising an open area 304C.Preferably, the dimple voids 304 occupy a total area that is at leastabout 25% of the total area of the wound contact surface 310. Morepreferably, the total dimple void area occupies at least about 50% ofthe total wound contact surface area. The dimple voids 304 are partiallydefined by sidewalls 308. The sidewalls 308 provide rigidity to helpresist compaction of dimple wound contact device 300 under compressiveforces created by suction or by securing the wound contact device 300 incontact with the wound. The wound contact elements 306 are generallyflat. However, in an embodiment, each wound contact element 306 may beconstructed to provide an arcuate contact surface having a radius ofcontact between about 0.1 mm to about 1 mm.

Dimple voids 304 can be formed in a variety of regular or irregularshapes, such as illustrated in FIGS. 1S, 3A, 5A, 7, and 8. In anembodiment, the voids 304 can be constructed so that they are not“undercut.” Such that the dimple voids 304 are no larger in nominaldiameter or circumference than their corresponding apertures 312. (Anundercut void would be characterized by the size of the apertureopening, as measured, e.g., by the diameter or circumference for agenerally circular aperture, being smaller than the size of thecorresponding inner void. For non-circular apertures and voices, anotherrelevant dimension can be used, such as perimeter or average width.”

In an embodiment, the structured material 302 of the wound contactdevice 300 is formed from Masterflo®. In another embodiment, thestructured material 302 is formed from polyester needle felt. Thestructured material 302 has a thickness in the range of about 1.0 mm toabout 1.5 mm. The dimple voids 304 are formed I the material 302, thedimple voids 304 having an average depth of about 0.75 mm and an averagediameter of about 2 mm. The dimple voids 304 may be formed into thematerial 302 prior to attachment of the wound contact layer 320, or thewound contact layer 320 can be attached to the material 302 first andthe voids 304 subsequently formed through the wound contact layer 320(to created the apertures 312) and further into the material 302 (tocreate the dimple voids 304).

The wound contact device 300 is replaced periodically, usually afterbeing in place on the wound for time periods ranging from several hoursto a few days. Because tissue growth preferentially occurs in theregions of the voids 304 compared with the regions of the wound contactelements 306, the dimple voids 304 and wound contact elements 306 of areplacement wound contact device 300 are preferably not positioned to begenerally aligned with the regions where the dimple voids 304 and woundcontact elements 306 of the previous wound contact device 300 had been.Thus, in order to encourage the generation of new tissue across allregions of the wound, several techniques can be employed to vary thepositioning of the dimple voids 304 and contact elements 306 within thewound. In an example, the dimple voids 304 can be arranged randomly sothat dimple voids 304 will not be aligned from one portion of woundcontact device 300 to another. In another example, wound contact devices300 can be provided with dimple voids 304 having different diameters,either within the same wound contact device 300 or between successivewound contact devices 300. In yet another example, wound contact devices300 can be provided with dimple voids 304 having a different spacing,either within the same wound contact device 300 or between successivewound contact devices 300.

As illustrated in FIGS. 3B and 3C, the dimple voids 304 are blinded inthe structured material 302, extending only partway through the material302 from the wound contact surface 310. In a variation of the woundcontact device 300, the dimple voids 304 and corresponding contactelements 306 are disposed on both the top and bottom sides of thedimpled wound contact device 300, i.e., the contact device 300 hasdimple voids 304 and wound contact elements 306 that are both proximaland distal to the wound surface when the contact device 300 is incontact with a wound. In another variation, some or all of the dimplevoids 304 traverse the entire thickness of the structured material 302.

When using the wound contact device 300, the dimple voids 304 can bepartially filled with therapeutic substances. For example, antisepticsubstances might be placed in voids 304 for treating infected wounds.Further, biologic healing agents could be delivered in the voids 304 toimprove the rate of new tissue formation. Additionally, the woundcontact device 300 could have a different function on each side. In anexample, one side of the contact device 300 could be optimized for thegrowth of new tissue, while the other side of the contact device 300could be optimized for the delivery of anti-microbial agents. In anotherexample, one side of the contact device 300 could have small gaps orroughened areas optimized for debriding necrotic tissue from a wound andthe other side of the contact device 300 could have contact elements 306having a smooth contact surface 310 for preventing entanglement of newtissue growth.

As shown particularly in FIGS. 3A and 3D, the wound contact layer 320comprises a thin impermeable film attached to a side of the structuredmaterial 302 to form a wound contact surface 310 including the woundcontact elements 306 and interposed apertures 312 corresponding to thedimple voids 304. The impermeable film is preferably a polyester filmmade form the resin Polyethylene Terephthalate (PET) such as sold undertrademark Mylar®. Other film materials may be used, including but notlimited to silicone, cellulose acetate, vinyl, urethane, or poly lacticacid. The film of the contact layer 320 is relatively thin compared withthe permeable material 302 into which the voids 304 extend. Availablefilms having a thickness of less than about 0.020 inches (0.51millimeters) are generally satisfactory, and films having a thickness ofless than about 0.004 inches (0.102 millimeters) are preferred. In anembodiment, a film having a thickness of about 0.0005 inches (0.0127millimeters) is used. The film has a generally smooth surface withminimal gaps or openings into which tissue can grow and becomeentangled. Thus, because nearly all tissue growth is into the voids 304,the wound contact device 300 can be pulled off of the wound with verylittle tissue disruption and with minimal discomfort to the patient.

The wound contact surface 310 comprising the film layer 320 can be madeeven more releasable from the healing wound tissue by applying acoating, such as a hydrogel, to the wound contact layer 320. In apreferred embodiment, the film is a plastic film and a polymerichydrogel is cross-linked with the plastic film to form a hydrogellaminate that resists de-lamination and potential retention of the gelin the wound when the wound contact device 300 is removed and changed.The gel provides the wound contact layer 320 of the contact device 300with a cool, wet, and slippery contact surface 310 that allows the woundcontact device 300 to be removed from the wound with minimal tissuedisruption and discomfort.

In an embodiment, the film layer 320 can comprise a dissolvable film.One or more drugs and other agents can be integrated to the dissolvablefilm. When the film dissolves in the presence of moisture, the drug oragent is released.

As shown particularly in FIG. 6, a wound contact device 600 comprises astructured material 602 and a wound contact layer 620 on a side of thematerial 602. The wound contact layer 620 comprises a thin sheet ofpermeable non-woven fabric attached to the structured material 602 toform a wound contact surface 610 including wound contact elements 606and interposed apertures 612 corresponding to dimple voids 604 thatextend into the material 602. The permeable sheet of fabric is highlycalendered by pressing the fabric between rollers or plates to produce agenerally uniform or glazed surface having a mean surface roughness withgaps in the range of about 0 microns to about 200 microns. Because ithas small surface gaps or roughened areas, a contact device 600 havingthe contact layer 620 can be advantageously applied in stages of woundhealing, when there is a benefit from allowing some tissue intertwiningwith the wound contact device 600. In particular, necrotic tissue may befound initially in some wounds. Necrotic tissue is preferably debridedout of the wound when the wound contact device is changed. Accordingly,in the early stages of wound healing, dead or necrotic tissue can beremoved by providing a contact layer 620 that promotes adherence of suchtissue, which is then removed when the wound contact device 600 is takenfrom the wound. The resulting removal of necrotic tissue encourages morehealthy new growth when a fresh wound contact device is applied.

A preferred fabric sheet for forming the contact layer 620 is aspunbonded (non-woven) low-lint 100% polyester fiber fabric, althoughother synthetic fabrics such as spunbonded polypropylene and spunbondedcomposite fibers can be highly calendered to sufficiently fine flatsurfaces. The fabric preferably has a thickness of less than about 0.020inches (0.51 millimeters), and more preferably has a thickness of lessthan about 0.004 inches (0.102 millimeters).

The respective properties of the different contact layers 620 and 320 inearly and late stage healing, respectively, make it advantageous toprovide a progressive healing kit containing one or more wound contactdevices 600 comprising the fabric contact layer 620 having small surfacegaps or roughened areas, along with one or more wound contact devices300 comprising the film contact layer 320 having essentially no surfaceirregularities or gaps. The wound contact devices in the kit may be usedto remove necrotic tissue earlier in the healing process with thecontact devices 600 comprising the fabric contact layers 620, and toreduce patient discomfort later in the healing process with the contactdevices 300 comprising the film laminate contact layers 320.

A dimpled contact device, such as the wound contact device 300, isillustrated by FIGS. 4A, 4B, and 4C. In particular, FIG. 4A shows awound surface 400 prior to application of the wound contact device, FIG.4B shows the wound surface 400 during application of the wound contactdevice, and FIG. 4C shows the wound surface after removal of the woundcontact device. The wound surface 400 can be a portion of a wound,including, for example, all or most of a shallow surface wound or asmall interior portion of a deep tissue wound. As shown in FIG. 4B, thewound contact elements 306 are in intimate contact with the woundsurface 400 while new tissue growth 410 protrudes from the wound surface400 into the dimple voids 302 of the wound contact device 300. The woundcontact device 300 can be pressed against the wound surface 400 bysuction or other means such as taping the contact device 300 to skinsurrounding the wound or wrapping a bandage over the contact device 300and the affected body part. As shown in FIG. 4C, when the wound contactdevice 300 is removed, the new tissue growth 410 is left intact.

As illustrated in FIGS. 5A and 5B, a rough irregular wound contactdevice 500 comprises a structured material 502 and a roughened woundcontact surface 510 including irregular voids 504 interposed withirregular contact elements 506. The irregular contact elements 506 canact a “hook-like” members adapted to contact and stick to necrotictissue when the contact device 500 is placed in contact with the wound.When the contact device 500 is removed from the wound, the wound isdebrided of necrotic tissue, which stuck to the hook like protrusions506 and is removed from the wound. Removal of necrotic tissue is animportant part of healing wounds because necrotic tissue is a source ofnourishment for harmful bacteria.

Even after removal of the necrotic tissue, the wound may still beinfected, thus inhibiting healing. The material 502 of the wound contactdevice 500 can comprise an antimicrobial agent such as antimicrobialsilver, which is useful in killing bacteria. Removal of necrotic tissueand the killing of bacteria residing in the wound can help the woundtransition to the proliferative phase, when new tissue is formed.Continued use of the wound contact device 500 including an antimicrobialagent can maintain a low bacteria level in the wound and accelerate thehealing, encouraging growth and proliferation of new cells and tissue.New cell growth can further be encouraged by addition of other growthenhancing materials to the material 502 of the wound contact device 500.

As shown particularly in FIG. 5B, the irregular wound contact device 500has a random cross sectional profile of voids 504 and contact elements506. The material 502 of the contact device 500 may be made frompolyester felt or batting. In an embodiment, the felt is singed with hotair so that a percentage of the felt fibers melt to form a texturedsurface 520 with a number of hook-like elements 506. In anotherembodiment, the hook-like elements 506 can resemble those typically usedin hook and loop fabric fasteners. The roughened surface 510 of theirregular contact device 500 can also be formed by passing the material502 under convective heat at or about the melting point of the materialfrom which the material 502 is comprised. For example, polyestermaterials typically melt in a range from about 250° C. to 290° C. Apolyester felt material passed briefly under a convective heat sourceoperating in this temperature range will experience surface melting andsubsequent fusing of the polyester strands at its surface. The degree ofsurface melting can be controlled with temperature and exposure time toyield a surface 510 having a desired roughness exhibiting irregularvoids 504 and irregular contact elements 506. Although the irregularcontact device 500 is illustrated as having only one roughened surface510, both the upper and lower surfaces of the contact device 500 may besimilarly roughened. A wound contact device 500 having both opposedsides roughened would be useful, for example, in the treatment of anundermined wound.

As illustrated in FIG. 7, a wound contact device 700 comprises astructured material 702 and a plurality of wound contact elements 706defining void spaces 704, each wound contact element having a woundcontact layer 720. When the contact device 700 is placed into a wound,the contact layer 720 of the pedestal-like wound contact elements 706 isin contact with the wound surface, and the void spaces 704 remain clearfor tissue growth. The structured material 702 has sufficient resistanceto the compressive forces of therapeutic suction to maintain the emptyvoid spaces 704 about the wound surface when suction is applied to thewound. In an embodiment, the wound contact layer 720 comprises a thinfilm having minimal surface discontinuities or gaps, as described abovewith reference to the embodiment of FIGS. 3A to 3E. In anotherembodiment, the wound contact layer 720 comprises a thin sheet ofnon-woven fabric, as described above with reference to FIGS. 6A to 6D.In yet another embodiment the wound contact layer 720 is integral to andpart of the structured material 702.

As illustrated in FIG. 8, a wound contact device 800 comprises astructured material 802 having a plurality of generally square orrectangular voids 804 and a wound contact surface 810 comprising woundcontact elements 806. The wound contact surface 810 can be formed from awound contact layer 812.

Treatment with a wound contact device as described herein is mosteffective when the contact device is held in intimate contact with thewound surface. The contact device is preferably held with a pressure ofat least about 0.1 PSI (5 mm Hg). Typically, the wound area is sealedwith a conformable cover and suction is applied to the dressing underthe cover. The dimpled wound contact device 300 is particularlywell-adapted for application of suction, because the material 302 isadapted to retain its structure, including the voids 304 so as tomaintain empty space therein, under the compressive force of suction andin the presence of moisture and other wound exudates. The wound contactdevice 300 is disposed in the wound such that the wound contact surface310 is in contact with the wound surface and the voids 304 are openabove the wound surface, as generally depicted in FIG. 4B. Typically,suction is applied at a level ranging between about 0.25 PSI (12 mm Hg)and about 5 PSI (260 mm Hg). Preferably, suction is applied at a levelbetween about 0.67 PSI (35 mm Hg) and about 1.45 PSI (75 mm Hg). Theeffectiveness of suction can be further improved by applying a woundpacking material to the back of the wound contact device as part of thewound dressing. One such suitable wound packing material is described inU.S. patent application Ser. No. 10/981,119, filed on Nov. 4, 2004.

Case Study 1

Patient A is a 70 year old male with a Stage IV decubitus ulcer on theright hip with significant undermining. A wound contact device includingthe structured material and wound contact surface of the presentinvention was applied to the wound and an adhesive film was placed overthe wound and the wound contact device. A suction of about 1.1 PSI wasapplied beneath the adhesive film to impart a force upon the wound. Thesuction was maintained substantially continuously. The wound contactdevice was replaced every two to four days. After use of the woundcontact device for 30 days, the undermined portion of the wound hadvirtually healed and the area of the wound opening had decreased from 66square centimeters to 45 square centimeters. A split thickness skingraft was applied to the wound.

Case Study 2

Patient B is a 50 year old male with a fracture of the right ankle withexposed bone. A plate was used to reduce the fracture and a rectusabdominus free flap was performed to cover the exposed bone andhardware. The flap only partially survived resulting in an open woundwith exposed bone and hardware. A wound contact device of the presentinvention was applied to the wound and an adhesive film was placed overthe wound and the contact device. A force was applied to the contactstructure by the application of an ace bandage wrapped around the ankleand/or by the application of suction. The suction force was generallyapplied for about half of the day and the force of the bandage wrap wasmaintained for the remainder of the day. For a number of days, thebandage wrap was solely used to impart the force. When the force wasimparted by suction, a suction of between about 1 PSI and about 2 PSIwas used. In less than 2 weeks, new tissue had grown over the exposedhardware. Within 7 weeks, the wound area was reduced from 50 squarecentimeters to 28 square centimeters.

While preferred embodiments of the invention have been shown anddescribed herein, it will be understood that such embodiments areprovided by way of example only. Numerous variations, changes, andsubstitutions will occur to those skilled in the art without departingfrom the spirit of the invention. Accordingly, it is intended that theappended claims cover all such variations as fall within the spirit andscope of the invention.

1.-16. (canceled)
 17. A wound contact device for use in treating a woundwith suction, the wound contact device comprising a permeable materialand a wound contact layer on the permeable material, the wound contactlayer comprising a thin sheet of non-woven fabric forming a woundcontact surface, the wound contact device having a plurality of voidsextending through the contact layer into the permeable material anddefining wound contact elements on the wound contact surface.
 18. Thewound contact device of claim 17, wherein the voids are dimple voids andwherein the permeable material is resistant to compression when suctionis applied to the wound dressing in suction-assisted wound therapy suchthat the dimple voids maintain empty space into which tissue can growfrom the wound surface.
 19. The wound contact device of claim 18 whereinthe applied suction is at least about 0.1 PSI.
 20. The wound contactdevice of claim 19, wherein the applied suction is between about 0.25PSI and about 5.0 PSI. 21.-40. (canceled)
 41. A therapeutic device fortreating a wound in a mammal, the device being arranged to be broughtinto intimate engagement with tissue of the mammal at the wound and tobe held in place at least partially by suction, the device comprising acover and a dressing, the dressing comprising a permeable structure anda wound contact layer, the permeable structure comprising a firstsurface, a second surface and a plurality of interstices located betweenthe first surface and the second surface, the wound contact layer beingdisposed on the first surface, the dressing comprising a plurality ofvoids extending through the wound contact layer and into the permeablestructure, each of the plurality of voids being in communication with atleast some of the interstices, the wound contact layer being arranged tobe disposed in contact with the wound, the cover being disposed over thesecond surface to establish a confined space to which suction may beapplied to produce a compressive force, the voids being resistant tocollapse to maintain at least some empty space in them when the dressingis under the compressive force of the suction.
 42. The device of claim41 wherein the interstices are interconnected.
 43. The device of claim42 wherein the permeable structure comprises fibers.
 44. The device ofclaim 41 wherein the cover is conformable.
 45. The device of claim 41wherein the cover comprises an adhesive film for forming a conformableseal with the tissue of the mammal adjacent the wound.
 46. The device ofclaim 41 wherein the average width of the voids is at least 0.1 mm. 47.The device of claim 46 wherein the average width of the voids is withinthe range of about 0.5 mm and 10 mm.
 48. The device of claim 41 whereinthe average depth of the voids is greater than 0.1 mm when the suctionis applied.
 49. A wound contact device for use in treating a wound in aliving being with suction, the wound contact device comprising a coverand a dressing, the dressing comprising a permeable material and a woundcontact surface, the permeable material comprising a plurality ofinterstices, the wound contact surface comprising a plurality of voidsin communication with at least some of the interstices, the woundcontact surface being arranged to be in engagement with the woundsurface and wherein at least a portion of the wound contact surfaceadjacent the openings is resistant to tissue ingrowth.
 50. The woundcontact device of claim 49 wherein the voids are discrete.
 51. The woundcontact device of claim 50 wherein the permeable material is resistantto compression when suction is applied to the wound dressing such thatthe voids maintain empty space into which tissue can grow from the woundsurface.
 52. The wound contact device of claim 49 wherein the averagedepth of the voids is greater than 0.1 mm when the suction is applied.53. The wound contact device of claim 52 wherein the average depth ofthe voids is in the range of 0.2 mm to 5 mm when the suction is applied.54. The wound contact device of claim 49 wherein the average depth ofthe voids is in the range of 250 to 1000 microns when the suction isapplied.
 55. The wound contact device of claim 49 wherein theinterstices are in the range of 0-400 microns.
 56. The wound contactdevice of claim 49 wherein the contact surface comprises a film.